The ancient civilization ruled by caesars was the Roman Empire. The term "caesar" originally referred to Julius Caesar, who played a pivotal role in the transition from the Roman Republic to the Roman Empire. Following his assassination, the title became synonymous with imperial authority in Roman governance. The Roman Empire enjoyed vast territorial expansion and cultural influence, with its rulers, known as caesars, exercising significant power. The legacy of the caesars remains evident in modern governance and law, as well as in the cultural and historical narrative of Western civilization.